The present invention relates to calenders and analogous machines which employ roll assemblies, and more particularly to improvements in calenders with exchangeable rolls.
It is already known to install one or more rolls of an assembly of rolls in a calender in such a way that the end portions of at least one roll are held in bearings and the bearings are movable with the one roll between a first position in which the one roll cooperates with one or more neighboring rolls to treat webs or sheets of paper, textile material or the like and a second position in which the one roll is spaced apart from the neighboring roll or rolls. German Auslegeschrift No. 11 13 357 discloses a calender wherein the roll assembly comprises a centrally located main roll and a cluster of four additional rolls, two at a level above and two at a level below the main roll. The main roll has an elastomeric outer layer and is removably installed in the frame of the calender. To this end, the main roll is loosely held between the two upper and the two lower additional rolls, the upper additional rolls can be lifted above and away from the main roll and the lower additional rolls are mounted in the frame of the calender for rotation about fixed axes. Hydraulic cylinder and piston units are provided to normally bias the upper additional rolls downwardly toward the main roll. In order to remove the main roll from the frame of the calender, the upper additional rolls must be lifted above and away from the main roll, a wagon with a vertically movable trough-shaped support is moved below the main roll, the support is caused to move upwardly so as to lift the main roll off the lower additional rolls, and the wagon or its support is thereupon moved to withdraw the lifted main roll from the frame of the calender. A fresh or restored main roll is introduced into the calender by reversing the aforedescribed sequence of steps. In order to prevent axial displacements of the main roll relative to the wagon, the latter is provided with vertically adjustable centering cones which are mounted on pivotable beams.
The just described mode of removing a roll from the frame of a calender is feasible only when the removable roll is the main roll of an assembly of several rolls and if the remaining (additional) rolls are installed in the frame in a specific way, namely with the two lower additional rolls fixed, with the two upper additional rolls movable upwardly and away from the lower additional rolls, and with the main roll simply nested between the upper and lower additional rolls. Another drawback of the proposal in the German Auslegeschrift is that the trough is likely to damage the elastomeric layer of the main roll.